I would think they are trying to ban the part where these fan arts are being sold as they are claims of a copyrighted character. But I could be wrong. Should you find the article or the agreement with details on this, i am sure it explains it even better than just saying they are banning fan art.

What? So in the US and Japan your not allowed to simply draw what you like? =O It's not like people sell they're fan art... Thats ridiculous, I'm not sure if this law will actually impact that much fan art drawers living in the US and Japan though. I mean, it's just fan art. What are they going to do? Hunt you down and put you in prison? Ah well, good thing I live in Canada.

Actually the selling of fanart as the work of the author is one of the reasons this could be going on since you tend to come across somethings on ebay claiming the author drew this and that here and there its probably not just centered around ebay if their considering a law for it.